Filters

Pearls of Weber

A collection of posts by David Weber containing background information for his stories, collected and generously made available Joe Buckley.

Posted by David at 12:00am

Maneuver, combat and missiles

Series: Honorverse

Date: October 22, 2002

Okay, here's the bottom line (in 5 minutes or less) on rolling ship,
missile attack angles, and The Meaning of the Universe.

(1) The very first line of defense against enemy fire is your ship's
electronic warfare capability. I'm not talking about stealth capabilities here, although
those are obviously important (you can't shoot something you don't know is there to shoot at,
after all), but more about fire confusion, decoys, jammers, etc. Anything and everything
to futz up your opponent's fire control. At missile ranges, even with the stand-off
capability of a laser head, even small errors in a fire control solution or your weapons'
tracking ability will have major consequences.

Advantage: Manticore

(2) The next line of defense are your active defenses: counter
missiles, laser clusters, and other energy weapons. Obviously, these systems prioritize
threats and engage them in order of priority. One reason that counter-missile ranges are
so short is because tradtional missiles, even with lowest-accel/max-endurance drive
settings, take only 180 seconds to reach the target (assuming they're coming in under
power), and it takes at least a little time for the computers to sort out the real threats
and target them. So there's not much point in having a really long-ranged
counter-missile (against those traditional missiles, he qualified innocently).
What you need is one with plenty of accel to get out and nail the incoming as soon as you
can generate a firing solution.

The laser clusters are to clean up the misses, and they are both
more and less effective than missiles. They are more effective in that, at their
engagement ranges, if you can see the target, you can hit the target virtually 100% of the
time. They are less effective in that they cannot penetrate a missile's impeller wedge,
which means that to score a hit, they must be able to fire down its throat, up its kilt,
with an almost perfect broadside shot, or after its wedge has gone down but before it
detonates. however, this is offset to a considerable extent by the fact that all
HH universe missiles are seeking weapons and their sensors (which are considerably weaker
than an all-up starship can mount on-board) have to have a clear look at what they're
seeking, which means that they have to keep the throat of their wedge pointed at the
target--if not continuously, as least for a constant series of "pop up" looks.
This is only exacerbated by the fact that most combatants, in searching for the maximum
"oomph" from their weapons, select the highest accel drive setting they can get
away with for a given range. This equates to the shortest effective flight time,
which tends to cut down on the missiles' ability to pursue anything but very direct (i.e.,
facing the target) flight profiles.

In addition to counter-missiles and laser clusters, warships
routinely use their main battery energy weapons in the anti-missile mode if there are
currently no enemy warships in energy range. The "rate of fire" on such heavy
weapons is much lower than for laser clusters, but they are longer ranged. Traditionally,
the SKM has been relatively comfortable with the performance of its counter-missiles in
the long-range interception role, and it has optimized its main battery fire control for
ship-to-ship engagements. The People's Navy, on the other hand, has never been as happy
with its counter-missile capability and so has accepted larger and more massive fire
control arrangements to give its main batteries better targeting discrimination against
very small targets in the missile engagement range. (Which could also have a few
implications for LAC engaging, too, now couldn't it?)

Advantage Missiles: Manticore

Advantage Laser Clusters: Neither

Advantage Main Battery: Peeps

(3) Sidewalls & the Wedge. Between them, these constitute the
third line of defense, although they are the primary passive defense. Sidewalls
will resist burn-through by current generation laser heads at anything much above
20,000-30,000 km, which is why the critical engagement ranges are so short. The impeller
wedge itself will resist penetration by any currently known weapon. Because of this, point
defense ignores any incoming weapon which tracking predicts will be unable to achieve an
effective firing angle against the sidewall from within 30,000 km. One thing you must bear
in mind is that the geometry of the wedge/sidewall/warship equation actually makes this a
relatively tiny target. Consider: an SD's impeller wedge is 300 km across, but the ship
herself has a maximum beam of less than a kilometer. She therefore represents a very small
(relatively speaking) aiming point at the middle of a very wide roof and floor of
impenetrable "armor." The sidewall is normally generated at a range of less than
10,000 meters from the actual ship, which means that, in the case of our SD from
the example above, the sidewall will be 143 kilometers inside the outer
"edges" of the wedge. There is thus a very considerable "tunnel"
effect, which requires an attacker (enemy warship or missile) to achieve an almost perfect
firing angle before it can even engage the sidewall, much less the ship.

Against enemy warships, this means, in effect, that no one can shoot
you (broadside to broadside, at any rate) with energy weapons unless you can shoot back at
him. It also means that it is very difficult for missiles to attain a firing
angle in the first place, which is why they tend to be fired in such large numbers.

The throat of the wedge for an SD is about
190 kilometers deep; the after aspect's opening is only about 40 kilometers deep. This is
why the throat is the most vulnerable aspect, and why missiles are usually
programmed to try to get around their targets in order to achieve a down-the-throat shot.
Usually, however, the target of the missile attack will turn to present its heavier
broadside point defense to the enemy fleet in order to engage missiles as they try to
attain that sort of firing position. In addition, of course, an entire task force will be
organized into one or more missile defense nets whose units protect one another.

In addition, a ship can shift position somewhat within the area of
its wedge. One can predict exactly where a ship will be within the volume of its wedge if
it is seeking to attain the maximum possible acceleration (assuming that one has solid,
reliable numbers on its inertial compensator's performance envelope), but at lower
accelerations, ships can move "off center" within their wedges.

"Rolling ship" is thus a maneuver which is intended to
turn a very narrow zone of vulnerability away from threat. It is a complete defense
against direct energy fire, and a major defense against missiles not simply because it
intercepts their direct fire but because it prevents the missiles' sensors from attaining
hard locks on the ships within the wedges. At the relative velocities resulting from most
missile fire control solutions, the laser head is always going to have a snap shot, with
very little time to compute and adjust firing angles, as it crosses the
sidewall/throat/kilt of a wedge, and if it doesn't know exactly where to find its target
in the instant that the shot is available, it will miss.

Note that most of the above applies to single-ship duels or
engagements with relatively low numbers of ships and relatively unencumbered
maneuverability on either side. In formal wall-of-battle engagements, the defensive
fleet's situation is both less flexible and less vulnerable. Because contact between
wedges is lethal, ships must maintain a safe separation (usually the width of the widest
wedge involved) from one another. A really well drilled fleet, however, with a CO who's
willing to (a) trust his people's abilities and (b) take a few risks, can cut that
separation in half, which has two major effects in defending against an opponent's missile
fire. (1) The relative positions of the units in a vertically-stacked wall which has
turned "up on its side" relative to the enemy mean that those ships at the
center of the wall are almost entirely protected from any missiles more than a couple of
hundred kilometers from them by the interposed wedges/sidewalls/hulls of the ships
"above" and "below" them; and (2) simply turning the wall's units on
its side builds a "road block" of wedges which the missiles must penetrate
before they can engage at all. If a wall of SDs stacked four high with an
impeller-roof-to--floor separation of 500 kilometers, a broadside separation of 150
kilometers and an ahead-and-astern separation of 200 kilometers turns up on its side, any
missile which wants to attack will have to achieve a down-the-throat/up-the-kilt
attack position or thread its way through a suddenly much constricted series of
"holes in the wall" to get at the sidewalls. The traditional formation for a
wall which has rolled ship is for the ships of the wall to do so at slightly offset
angles. This increases the number of firing aspects from which missiles could expect to
hit something, but it also makes the broadside point defense capability of ships in other
tiers of the wall available to protect the exposed units at its "top" and
"bottom." In addition, light screening units hidden on the far side of the wall
from the enemy but taking missile intercept data from ships in the wall and/or recon
drones deployed to see around the wall can also supply indirect defensive fire
(counter-missiles) from a position in which they are relatively invisible (and so
invulnerable to) the seekers of incoming missiles.

Advantage: probably a small one to the SKM because of the edge the
FTL com and its generally superior electronics give to the screening units in
"hidden" positions and the generally (but not always) higher level of
proficiency which normally allows Manty admirals to maintain a tighter separation in their
wall formations.

(4) Particle Shielding/Radiation Shielding. These are the final
defense against hostile fire, short of the structure of the ship itself. There is very
little to choose between Manty and Peep technology in these areas. However, these defenses
are always tougher, for virtually every navy, against head-on, down-the-throat shots. This
is not only because down-the-throat shots are the must dangerous from the perspective of
enemy targeting capability, but also because they have to be stronger in those
areas simply because normal impeller-drive movement is going to place the greatest strain
on them.

Advantage: neither

The rate of turn for an impeller-drive ship outside a wall of battle
is fairly high, although it is considerably higher for a smaller ship than for a larger
one. A typical SKM DD can alter her heading (but not necessarily her vector, of
course) by 90 degrees in about 100 seconds; an SD would need about twelve minutes for a
90-degree turn. (The difference in roll rates is not as a great, although it also favors
the smaller ship by a largish margin. In addition, of course, a smaller ship, with a lower
beam and a narrower wedge, can roll "further" in a given length of time with the
same roll rate than a larger ship can.) And as someone pointed out in connection with the Bellerophon
in SVW, however, how far you have to turn to deny a shot to an enemy is entirely
a function of range-to-target, so even a relatively low absolute turn rate can take away a
shot if it starts soon enough and the range is long enough. Remember also that sidewalls
extend the full length of the wedge, creating a protected "box" within the wedge
from its front edge to its rear edge. It is not necessary to turn 90 degrees away from an
opponent to deny him a down-the-throat shot; all you have to do is turn far enough that
your sidewall--which is no more than 10 km from the side of your ship--is interposed.